1. Field of the Invention
The present general inventive concept relates to an inkjet printing device, and more particularly, to an inkjet printing device to generate ultrafine droplets and a method of driving the same.
2. Description of the Related Art
Inkjet printing devices are used to eject fine droplets of ink onto desired positions of printing media in order to print predetermined images. The inkjet printing devices have lately been applied to a larger variety of fields, for example, flat panel displays (FPDs) such as liquid crystal displays (LCDs) and organic light emitting displays (OLED), flexible displays such as electronic papers (e-papers), printed electronics such as metal interconnection lines, and organic thin film transistors (OTFTs). Among process techniques for applying the inkjet printing devices to display devices or printed electronics, more attention must be paid to developing high-resolution ultrafine printing techniques.
Inkjet printing devices may be classified into piezoelectric inkjet printing devices and electrostatic inkjet printing devices depending on how the ink is ejected. Specifically, the piezoelectric inkjet printing devices eject ink by deforming a piezoelectric material, while the electrostatic inkjet printing devices eject ink using electrostatic force. Also, the electrostatic inkjet printing devices may operate based on the following two methods. First, ink droplets may be ejected using electrostatic induction. Second, charged pigments may be accumulated using electrostatic force and ink droplets may be then ejected.
In the case of a piezoelectric inkjet printing device, since ink is ejected by a drop on demand (DOD) technique, controlling printing operation and driving the inkjet printing device is easy. Also, the piezoelectric inkjet printing device generates ejecting energy by mechanically deforming a piezoelectric material and any type of ink may be used. However, the piezoelectric inkjet printing device can neither produce ultrafine droplets with a size of several picoliters or less nor allow ink droplets to exactly reach a desired position as compared with an electrostatic inkjet printing device. In contrast, the electrostatic inkjet printing device may produce ultrafine droplets, is easy to drive, and allows ink to be ejected in a desired direction, so that the electrostatic inkjet printing device is quite appropriate for a precise printing process. However, since forming separate ink flow paths in an electrostatic inkjet printing device using an electrostatic induction technique is difficult, ink cannot be easily ejected via a plurality of nozzles by DOD. Also, when charged pigments are accumulated due to an electrostatic force, necessitated by accumulating highly dense pigments, the ejection rate of ink droplets and the type of ink are limited.